Christopher Reeve was known as much for athleticism as for dramatic talent, until a 1995 riding accident changed everything. Paralyzed from the neck down, he is now known mostly for other things, like courage, optimism and personal integrity.

His squeaky-clean image has served Mr. Reeve well in his role as an advocate for the handicapped. And it has also made him a natural for Madison Avenue, and for advertisers hungry to benefit from his reputation. In the few endorsements and commercial appearances he has made thus far, Mr. Reeve has affixed his credibility to the products he promotes.

But these are dangerous waters, indeed, and occasionally quite the juggling act, too. (Just ask Kathie Lee Gifford about knowing your product before giving it your name.) For Mr. Reeve, navigating the tides of commercialism while maintaining his clean-cut reputation may be particularly challenging, especially now that he has decided to add commercial directing to his repertory, in a deal with a Manhattan production house, TAG Pictures Inc., announced last month.

How exactly does he propose to do it? By choosing carefully, and by offering his services -- and his image -- only to those companies he decides are worthy of them.

"I really think that in the future," he said, "the public is going to want a really high ethical standard from corporate America." That is especially so, he said, for companies that "need to overhaul their image because they are mistrusted by the public, like pharmaceutical companies, insurance companies and chemical companies."

"My job will be to get the client to look at the goods and services they provide, see that they are really useful and valuable, and then develop a campaign to communicate that message to the public."

Of course, most American television viewers do not have the slightest idea who is directing the spots they watch. For his commercials, at least, Mr. Reeve and his clients would presumably be changing that, publicizing his involvement and putting his name on a client's product, as it were, even when he is not necessarily also lending his appearance.

"It's almost like he plans to create a Christopher Reeve brand for the things he advertises," said Beth E. Barnes, an assistant professor at the Newhouse School of Public Communications at Syracuse University and chairwoman of its advertising department. "Something like a Good Housekeeping Seal of Approval."

But Good Housekeeping has its test kitchens. What, other than good faith, qualifies Mr. Reeve to endorse a product, either overtly or implicitly? And what happens if he makes a mistake?

There are, after all, those who say that Mr. Reeve has already erred at least once by appearing in a spot by Fallon McElligott, a unit of Publicis, for Nuveen Investments that was shown during this year's Super Bowl. The commercial, which Mr. Reeve did not direct, showed him "walking" by virtue of computer animation, all the while promoting "new ways" of thinking and scientific advances that he said might soon cure him.

Many advocates for the handicapped were aghast, maintaining that no such cure is in the offing, and that the spot cruelly offered false hope to people who should be concentrating on adapting to life with their disabilities. Charles Krauthammer, a Pulitzer Prize-winning columnist who is also a doctor and has paralysis, took Mr. Reeve to task in February in Time magazine for the Nuveen commercial and remains skeptical about a cure, as does Paul K. Longmore, a childhood polio victim and a disability expert at San Francisco State University.

"What if I had waited for this cure instead of learning to live?" asked Professor Longmore, who says that a cure -- if that is the right term -- is, at best, a long way off. "I would have ended up in a state of suspended animation."

But Mr. Reeve, who as yet has no clients in his arrangement with TAG, is confident that he has the ability to adequately assess the merits of those who may seek to use his services. He is unrepentant about the Nuveen ad, insisting that there is "genuine reason for optimism" about a cure and that he has scientific information that others do not, given to him before it is published in scientific journals on condition that he keep it a secret.

And he cites his experience so far with other commercials as further proof of his ability to choose wisely among prospective clients.

For example, Mr. Reeve has already done some directing -- a series of corporate image commercials for Johnson & Johnson in which he appeared with the songwriter Randy Newman, the actor Ray Romano and the author Toni Morrison. The spots, by McCann-Erickson Worldwide, a unit of the Interpublic Group, highlighted values like hope, tenacity and -- in the case of Mr. Reeve -- faith. "I learned an important lesson," he says in his commercial. "My disability need not be disabling."

And he is also the principal spokesman for HealthExtras, a Rockville, Md., disability insurance concern with which he signed a five-year contract earlier this year. He only undertook his role, in a $25 million campaign by Focused Image, an Alexandria, Va., agency, after doing what he said was a great deal of research.

"I thoroughly investigated the company," he said. "I have a real responsibility."

That may be. But if one or more of Mr. Reeve's future investigations prove inadequate, the consequences may be dire indeed.

"The first time he picks wrong, he's going to be in a lot of trouble," Professor Barnes said. "Once he makes a mistake, people may decide that they're not going to believe him about anything any more."